Do-it-yourself false monitor repair

In detail: do-it-yourself false monitor repair from a real master for the site my.housecope.com.

Today I want to share with you the experience of repairing a monitor with my own hands. I repaired my old one LG Flatron 1730s... Like this:

This is a 17 "LCD monitor. I must say right away that when there is no image on the monitor, we (at work) immediately refer such copies to our electronics engineer and he deals with them, but there was an opportunity to practice 🙂

To begin with, let's understand the terminology a little: earlier, CRT monitors (CRT - Cathode Ray Tube) were in use. As the name implies, they are based on a cathode ray tube, but this is a literal translation, it is technically correct to talk about a cathode ray tube (CRT).

Here is a disassembled sample of such a "dinosaur":

Nowadays LCD type of monitors (Liquid Crystal Display - display on the basis of liquid crystals) or simply LCD is in vogue. These designs are often referred to as TFT monitors.

Although, again, if we speak correctly, then it should be like this: LCD TFT (Thin Film Transistor - screens based on thin-film transistors). TFT is simply the most widespread variety, more precisely, LCD (liquid crystal) display technology.

So, before we start repairing the monitor ourselves, let's consider what “symptoms” did our “patient” have? In short: there is no image on the screen... But if you look a little more closely, then various interesting details began to emerge! 🙂 When turned on, the monitor showed an image for a split second, which immediately disappeared. At the same time (judging by the sounds), the system unit of the computer itself worked properly and the operating system was loaded successfully.

Video (click to play).

After waiting for a while (sometimes 10-15 minutes), I found that the image appeared spontaneously. Repeating the experiment several times, I was convinced of this. Sometimes for this, however, it was necessary to turn off and turn on the monitor with the "power" button on the front panel. After resuming the picture, everything worked without interruptions until the computer was turned off. The next day, history and the whole procedure were repeated again.

Moreover, I noticed an interesting feature: when the room was warm enough (the season is no longer summer) and the batteries were heated fairly, the idle time of the monitor without an image was reduced by five minutes. There was a feeling that it warms up, reaching the desired temperature regime and then works without problems.

This became especially noticeable after one day the parents (the monitor was with them) turned off the heating and the room became quite fresh. In such conditions, the image on the monitor was absent for about 20-25 minutes, and only then, when it got hot enough, did it appear.

According to my observations, the monitor behaved exactly like a computer with certain problems of the motherboard (capacitors that have lost capacity). If it is enough to warm up such a board (let it run or direct a heater towards it), it normally “starts up” and, quite often, works without interruptions until the computer is turned off. Naturally, this is - until a certain moment!

But at the early stage of diagnosis (before opening the patient's case), it is highly desirable for us to make the most complete picture of what is happening. According to it, we can roughly navigate in which node or element is the problem? In my case, after analyzing all of the above, I thought about the capacitors located in the power supply circuit of my monitor: we turn on - there is no image, the capacitors are warming up - it appears.

Well, it's time to test this assumption!

Let's disassemble! First, using a screwdriver, unscrew the screw that secures the bottom of the stand:

Then, - remove the corresponding screws and remove the base of the stand attachment:

Next, using a flat-tipped screwdriver, we pry the front panel of our monitor and in the direction indicated by the arrow, we begin to carefully separate it.

Slowly, we move along the perimeter of the entire matrix, gradually removing the plastic latches holding the front panel from their seats with a screwdriver.

After we disassembled the monitor (separated its front and rear parts), we see the following picture:

If the “insides” of the monitor are attached to the back panel with adhesive tape, peel it off and remove the matrix itself with the power supply and control board.

The back plastic panel remains on the table.

Everything else in the disassembled monitor looks like this:

This is how the “filling” looks in the palm of my hand:

Let's show a close-up of the panel of settings buttons that are displayed for the user.

Now, we need to disconnect the contacts connecting the cathode backlight lamps located in the monitor matrix with the inverter circuit responsible for their ignition. To do this, we remove the aluminum protective cover and see the connectors under it:

We do the same on the opposite side of the monitor's protective casing:

Disconnect the connectors from the monitor inverter to the lamps. Who cares, the cathode lamps themselves look like this:

They are covered on one side with a metal casing and are located in it in pairs. The inverter “lights up” the lamps and adjusts the intensity of their light (controls the brightness of the screen). Now, instead of lamps, LED backlights are increasingly used.

Advice: if you find that on the monitor suddenly the image is gone, take a closer look (if necessary, illuminate the screen with a flashlight). Perhaps you will notice a faint (faint) image? There are two options here: either one of the backlight lamps is out of order (in this case, the inverter simply goes “in defense” and does not supply power to them), remaining fully operational. The second option: we are dealing with a breakdown of the inverter circuit itself, which can either be repaired or replaced (in laptops, as a rule, they resort to the second option).

By the way, the laptop inverter is located, as a rule, under the front outer frame of the screen matrix (in the middle and bottom of it).

But we got distracted, we continue to repair the monitor (more precisely, for now, chick it) 🙂 So, having removed all the connecting cables and elements, we disassemble the monitor further. We open it like a shell.

Inside we see another cable connecting, protected by another casing, the matrix and monitor backlight lamps with the control board. Peel off the scotch tape up to half and see under it a flat connector with a data cable in it. We carefully remove it.

We put the matrix separately (we will not be interested in it in this repair).

This is how it looks from the back:

Taking this opportunity, I want to show you the disassembled monitor matrix (recently they tried to repair it at work). But after analysis, it became clear that it would not be possible to fix it: some of the liquid crystals on the matrix itself burned out.

In any case, I shouldn't have seen my fingers behind the surface so clearly! 🙂

The die is secured in a frame that holds and holds all of its parts together using snug plastic snaps. In order to open them, you will have to work thoroughly with a flat screwdriver.

But with the type of do-it-yourself monitor repair that we are doing now, we will be interested in another part of the design: the control board with the processor, and even more so, the power supply of our monitor. Both of them are shown in the photo below: (photo - clickable)

So, in the photo above, on the left, we have the processor board, and on the right, the power board combined with the inverter circuit. A processor board is often referred to as a scaler board (or circuit).

The scaler circuit processes the signals coming from the PC. In fact, a scaler is a multifunctional microcircuit, which includes:

microprocessor
a receiver (receiver) that receives a signal and converts it into the desired form of data, transmitted via digital interfaces for connecting a PC
an analog-to-digital converter (ADC) that converts the input analog R / G / B signals and controls the resolution of the monitor

In fact, a scaler is a microprocessor optimized for the task of image processing.

If the monitor has a frame buffer (random access memory), then work with it is also carried out through the scaler. For this, many scalers have an interface for working with dynamic memory.

But we - again distracted from the repair! Let's continue! 🙂 Let's take a close look at the monitor power combo board. We will see such an interesting picture there:

As we assumed at the very beginning, remember? We see three swollen capacitors requiring replacement. How to do it correctly is described here in this article of our site, we will not be distracted once again.

As you can see, one of the elements (capacitors) swelled not only from above, but also from below, and some of the electrolyte flowed out of it:

To replace and effectively repair the monitor, we will need to completely remove the power board from the casing. We unscrew the fastening screws, take out the power cable from the connector and take the board in our hands.

Here is a photo of her back:

I want to say right away that quite often the power board is combined with the inverter circuit on one PCB (printed circuit board). In this case, we can talk about a combination board, represented by the power supply of the monitor (Power Supply) and the inverter of the backlight (Back Light Inverter).

In my case, this is exactly the case! We see that in the photo above, the lower part of the board (separated by a red line) is, in fact, the inverter circuit of our monitor. It happens that the inverter is represented by a separate PCB, then there are three separate boards in the monitor.

The power supply (the upper part of our PCB) is based on the FAN7601 PWM controller microcircuit and the SSS7N60B field-effect transistor, and the inverter (its lower part) is based on the OZL68GN microcircuit and two FDS8958A transistor assemblies.

Now we can safely start repairing (replacing capacitors). We can do this by conveniently placing the structure on the table.

This is how the area of interest to us will look after removing faulty elements from it.

Let's take a close look at what nominal capacitance and voltage do we need to replace the elements soldered from the board?

We see that this is an element with a rating of 680 microfarads (mF) and a maximum voltage of 25 volts (V). In more detail about these concepts, as well as about such an important thing as maintaining the correct polarity when soldering, we talked with you in this article. So, let's not dwell on this again.

Let's just say that we have failed two 680 mF capacitors with a voltage of 25V and one at 400 mF / 25V. Since our elements are connected in parallel to the electrical circuit, we can safely use two 1000 mF capacitors instead of three capacitors with a total capacity (680 + 680 + 440 = 1800 microfarads), which will add up to the same (even greater) capacitance.

The capacitors removed from our monitor board look like this:

We continue to repair the monitor with our own hands, and now it is time to solder the new capacitors in place of the removed ones.

Since the elements are really new, they have long “legs”. After soldering in place, just carefully cut off their excess with side cutters.

As a result, we got it like this (for the sake of order, for two 1000 microfarad capacitors, I put an additional 330 mF element on the board).

Now, we carefully and carefully reassemble the monitor: fasten all the screws, connect all cables and connectors in the same way, and, as a result, we can proceed with an intermediate test run of our half-assembled structure!

Advice: there is no point in putting the entire monitor back together, because if something goes wrong, we will have to disassemble everything from the very beginning.

As you can see, the frame, signaling the absence of a connected data cable, appeared immediately.This, in this case, is a sure sign that the repair of the monitor with our own hands was successful with us! 🙂 Previously, until the malfunction was corrected, there was no image at all until it warmed up.

Mentally shaking hands with ourselves, we assemble the monitor to its original state and (for testing) we connect it with a second display to the laptop. We turn on the laptop and see that the image immediately "went" to both sources.

Q.E.D! We just repaired our monitor ourselves!

note: To find out what other types of TFT monitor malfunctions there are, follow this link.

That's all for today. I hope this article was helpful to you? See you next on the pages of our site 🙂

I didn't think that only our LG Flatron L1730S monitor is a long-liver, but nevertheless I was repaired once, and the replacement of capacitors and the repair of the monitor power supply cost five hundred rubles, that was about five years ago, I can't even imagine how much it costs to repair the monitor now ...

And now the malfunction at the monitor has appeared very incomprehensible, ...

And now the monitor malfunction has appeared very incomprehensible, at first it stopped turning on from standby mode, but one day the screen stopped completely lighting up when the computer was turned on.

The funny thing is, they thought that the system unit was faulty, while it was being disassembled and cleaned, the monitor stood to itself chuckling on the sidelines at the home grief - the masters. Disassembly cleaning the computer also did not work, but, as always, the Internet helped out, somewhere who already had a similar monitor malfunction.

The computer was connected to the TV, which worked normally all day. The monitor was connected to the netbook, it immediately refused to turn on, now it became clear that it needed repair. They did not carry it to the workshop, they decided to repair the monitor with our own hands, disassembling the monitor is very simple.

We remove the front panel, it is latched and screwed with two screws at the back and bottom

And now the monitor boards are visually available.

We carefully inspect the boards, looking first of all for swollen capacitors, which must be replaced. If possible, then you need to check the capacitors with a device.

All the repair and disassembly of the monitor took about half an hour, not counting the purchase of capacitors (at a price of about twenty rubles). As a result, the monitor is fully functional - this is the only drawback of the LG Flatron L1730S, since I had to refuse to buy a new monitor!

Here are the TOP 10 most common LCD monitor malfunctions that I felt the hard way. The fault rating was compiled according to the author's personal opinion, based on the experience of working in the service center. You can take this as a universal repair manual for almost any LCD monitor from Samsung, LG, BENQ, HP, Acer and others. Here we go.

I divided the malfunctions of LCD monitors into 10 points, but this does not mean that there are only 10 of them - there are many more, including combined and floating ones. Many of the breakdowns of LCD monitors can be repaired by hand or at home.

in general, although the power indicator may be blinking. At the same time, twitching the cable, dancing with a tambourine and other pranks do not help. Tapping the monitor with a nervous hand usually doesn't work either, so don't even try. The reason for such a malfunction of LCD monitors is most often the failure of the power supply board, if it is built into the monitor.

Recently, monitors with an external power source have become fashionable. This is good because the user can simply change the power supply in the event of a breakdown. If there is no external power source, then you will have to disassemble the monitor and look for a malfunction on the board.In most cases, it is not difficult to disassemble an LCD monitor, but you need to remember about safety.

Before fixing the poor fellow, let him stand for 10 minutes, unplugged. During this time, the high-voltage capacitor will have time to discharge. ATTENTION! DANGEROUS TO LIFE if the diode bridge and the PWM transistor burn out! In this case, the high voltage capacitor will not discharge in an acceptable time.

Therefore, EVERYONE before repairing to check the voltage on it! If a dangerous voltage remains, then the capacitor must be manually discharged through an insulated resistor of about 10 kOhm for 10 seconds. If you suddenly decide to close the terminals with a screwdriver, then keep your eyes away from sparks!

Next, we proceed to inspect the monitor power supply board and change all burned-out parts - these are usually swollen capacitors, blown fuses, transistors and other elements. It is also MANDATORY to solder the board or at least inspect the soldering under a microscope for microcracks.

From my own experience I will say - if the monitor is more than 2 years old - then 90% that there will be microcracks in the soldering, especially for LG, BenQ, Acer and Samsung monitors. The cheaper the monitor, the worse it is made at the factory. Up to the point that the active flux is not washed out - which leads to the failure of the monitor after a year or two. Yes, yes, just when the guarantee ends.

when the monitor is turned on. This miracle directly indicates to us a malfunction of the power supply.

Of course, the first step is to check the power and signal cables - they must be securely fastened in the connectors. A blinking image on the monitor tells us that the monitor backlight voltage source is constantly jumping off the operating mode.

The most common reason for this is swollen electrolytic capacitors, microcracks in the solder and a faulty TL431 microcircuit. Swollen capacitors most often cost 820 uF 16 V, they can be replaced with a larger capacity and a higher voltage, for example, the cheapest and most reliable ones are Rubycon 1000 uF 25 V capacitors and Nippon 1500 uF 10 V capacitors. 105 degrees) Nichicon 2200 uF 25 V. Everything else will not last long.

after the time has elapsed or does not turn on immediately. In this case, again, three frequent LCD monitors malfunctions in order of frequency of occurrence - swollen electrolytes, microcracks in the board, faulty TL431 microcircuit.

With this fault, a high-frequency squeak of the backlight transformer can also be heard. It usually operates at frequencies between 30 and 150 kHz. If the mode of its operation is violated, oscillations can occur in the audible frequency range.

but the image is viewed under bright light. This immediately tells us about a malfunction of LCD monitors in terms of the backlight. In terms of the frequency of occurrence, it could be put in third place, but it has already been taken there.

Option two - either the power supply and inverter board burned out, or the backlight lamps are faulty. The latter reason is not common in modern monitors with LED backlighting. If the LEDs are backlit and fail, then only in groups.

In this case, there may be a darkening of the image in places at the edges of the monitor. It is better to start repairs with diagnostics of the power supply and inverter. An inverter is the part of the board that is responsible for the formation of a high-voltage voltage of the order of 1000 volts to power the lamps, so in no case should you try to repair the monitor under voltage. You can read about repairing the Samsung monitor power supply in my blog.

Most monitors are similar in design, so there shouldn't be any problems. At one time, monitors simply rained down with a breakdown in contact near the tip of the backlight. This is treated by the most careful disassembly of the matrix to get to the end of the lamp and solder the high voltage wires.

If the backlight itself burns out, I would suggest replacing it with the LED backlight bar that usually comes with your inverter.If you still have questions - write to me by mail or in the comments.

These are the nastiest LCD monitor malfunctions in the life of any computer technician and user, because they tell us that it's time to buy a new LCD monitor.

Why buy new? Because your pet's matrix is 90% unusable. Vertical stripes appear when the contact of the signal loop with the contacts of the matrix electrodes is broken.

This can only be cured by careful application of anisotropic adhesive tape. Without this anisotropic glue, I had a bad experience repairing a Samsung LCD TV with vertical stripes. You can also read how the Chinese repair such strips on their machines.

An easier way out of this unpleasant situation can be found if your brother-in-law friend has the same monitor lying around, but with faulty electronics. It will not be difficult to blind from two monitors of similar series and the same diagonal.

Sometimes even a power supply unit from a monitor with a larger diagonal can be adapted for a monitor with a smaller diagonal, but such experiments are risky and I do not recommend starting a fire at home. Here in someone else's villa - that's another matter ...

Their presence means that the day before, you or your relatives had a fight with the monitor because of something outrageous.

Unfortunately, household LCD monitors do not provide shockproof coatings and anyone can offend the weak. Yes, any decent poke with a sharp or blunt object into the LCD monitor matrix will make you regret it.

Even if there is a small trace or even one broken pixel, over time, the spot will begin to grow under the influence of temperature and voltage applied to the liquid crystals. Unfortunately, it will not work to restore the dead pixels of the monitor.

That is, there is a white or gray screen on the face. First, you should check the cables and try connecting the monitor to a different video source. Also check if the monitor menu is displayed on the screen.

If everything remains the same, we look closely at the power supply board. In the power supply unit of the LCD monitor, voltages of 24, 12, 5, 3.3 and 2.5 volts are usually formed. It is necessary to check with a voltmeter if everything is in order with them.

If everything is in order, then we carefully look at the video signal processing board - it is usually smaller than the power supply board. It has a microcontroller and auxiliary elements. It is necessary to check whether food comes to them. With one probe, touch the contact of the common wire (usually along the contour of the board), and with the other, go over the terminals of the microcircuits. Usually food is somewhere in the corner.

If everything is in order in the power supply, but there is no oscilloscope, then we check all the monitor loops. There should be no carbon deposits or darkening on their contacts. If you find something, clean it with isopropyl alcohol. In extreme cases, you can clean it with a needle or scalpel. Also check the ribbon cable and the board with the monitor control buttons.

If all else fails, then perhaps you are faced with a case of a failed firmware or a failure of the microcontroller. This usually happens from surges in the 220 V network or simply from aging of the elements. Usually, in such cases, you have to study special forums, but it's easier to start up for spare parts, especially if you have a familiar karate fighter fighting against objectionable LCD monitors.

This case is easily treated - you need to remove the frame or the back cover of the monitor and pull out the board with buttons. Most often, there you will see a crack in the board or in the solder.

Sometimes there are faulty buttons or a loop. A crack in the board violates the integrity of the conductors, so they need to be cleaned and soldered, and the board must be glued to strengthen the structure.

This is due to aging of the backlight lamps. According to my data, LED backlighting does not suffer from this. Deterioration of the parameters of the inverter is also possible due to aging of the constituent components.

This is often due to a bad VGA cable without an EMI suppressor - a ferrite ring.If replacing the cable does not work, then power supply interference may have entered the imaging circuits.

Usually they get rid of them schematically by using filtering capacities for power supply on the signal board. Try to replace them and write to me about the result.

This completes my wonderful rating of the TOP 10 most common LCD monitor malfunctions. Most of the breakdown data is collected from repairs of popular monitors such as Samsung, LG, BENQ, Acer, ViewSonic and Hewlett-Packard.

This rating, it seems to me, is also true for LCD TVs and laptops. What is your situation on the LCD monitor repair front? Write on the forum and in the comments.

The most common questions when disassembling LCD monitors and TVs - how to remove the frame? How do I release the latches? How to remove the plastic from the case? etc.

One of the wizards made a nice animation explaining how to disengage the latches from the chassis, so I'll leave it here - it will come in handy.

To view animation - click on the image.

Recently, monitor manufacturers are increasingly completing new monitors with external power supplies in a plastic case... I must say that this makes it easier to troubleshoot LCD monitors by replacing the power supply. But it complicates the operating mode and the repair of the power supply itself - they often overheat.

I showed how to disassemble such a body in the video below. The method is not the best, but it is fast and can be done with improvised means.

The LG monitor can fail for various reasons, in order to diagnose and be able to repair the device, it must first be disassembled. It is the disassembly process that causes difficulties for the owners, so we decided to write detailed instructions on how to disassemble the lg monitor. Depending on the specific model, this process may differ slightly, so in this review we will consider several options.

The first step is to remove the monitor stand;

Remove the back cover;

Carefully detach the front bezel of the monitor;

Detach the latches holding the matrix;

Remove metal plugs;

Remove the two connectors with the backlight cables;

The monitor matrix is connected to the board with a ribbon cable, before removing it, you must also disconnect it;

Electronic boards and power supply are now also available for disassembly, you can remove them too;

First, you need to unscrew the bolts holding the lg monitor delivery, its absence will provide access to the back cover. Before starting this simple task, the monitor must be laid on a flat surface in order to minimize the risks of damage to the screen itself. Usually the stand is fixed with four screws for a Phillips screwdriver, that is, it will not be difficult to remove it. In addition, the stands are equipped with plastic covers, which will have to be removed to get to the screws.The process of removing the back cover of the device is not much different from the previous one, in the same way we unscrew all the screws and remove it. After that, the cover can already be removed to the side, the easy part of the disassembly process ends there.If you are looking for an answer to the question of how to disassemble an lg monitor, go to the next step of the process, here you will need to remove the front frame of the technique. This process is very responsible and requires the utmost care from the performer. The fact is that the plastic on the front of the case is very thin, in addition, there is a possibility that you will damage the matrix of the device. That is why, armed with a thin, flat screwdriver, carefully open all the latches, and then remove the frame.After the front part of the case is removed, access to the plastic fasteners of the monitor matrix will open; they also need a special approach, even a slight damage to the screen will lead to its failure. Disassembling the lg flatron l1953s monitor does not imply removing the metal plugs, but if you have a different model, disconnect them, you can do it with your hands, it will take a little effort.Now the matrix can be removed, just do not make any sudden movements, you will also need to disconnect the screen cable that is connected to the board.The next step, for applicants on how to disassemble an lg flatron monitor, will be to disconnect the backlight terminals, usually there are two of them, but then again it all depends on the model of technology. You can remove the terminals without using any tools, although this requires a little effort, as is the case with plugs.Now you have access to the "brain" of the monitor, its microcircuits, as well as the power supply, by the way, most of the faults are associated with just one of these details. They are also fastened with bolts, by unscrewing them you can inspect the components for damage. In general, we received an answer to the question posed - how to disassemble the lg monitor.You can ask a question to the masters from our service center by calling by phone or by writing your question on the feedback form.Your message has been sent.You might also be interested inOrder a repair in our service center, and you will receive a working device on the same day, with a guarantee up to 1 yearWe increasingly often hear complaints about sudden breakdowns of LCD monitors, and most of them happen just like that, for no apparent reason. Most often they just "die" parts for monitors, moreover, simply because their resource has been exhausted. It turns out that the idea that every device has a time-bomb is not such a utopia.Take liquid crystal displays, for example. Here's why they should fail - they have no moving parts, or components that can burn out - only semiconductors. In monitors, the weak link may be CCFL lamps - luminescent, with a cold cathode, intended for matrix illumination. They really do not differ in durability, and, at first, their brightness decreases, and then they completely fail. You can replace them with more reliable LED lamps.Power sources can also give "slack". Even the most modern and super-sophisticated devices have a converter that divides 220 V into small voltages that are required for each circuit. Burnt out backlight inverter can extinguish the entire display, regardless of where and when it was produced. And then, there comes that not very beautiful day when the monitor does not turn on. In this case, it does not matter whether the power-on indicator is on or not, but the image on the screen does not appear.The easiest way to fix a monitor, which power source is a separate box or plug adapter, than the one with which it is hidden inside the case. Indeed, in the first case, you can simply change the burned-out parts for monitors, finding similar power sources from old equipment in the bins, or buy spare parts for the monitor at the nearest radio market.There is no need to disassemble the display case, so even a beginner can handle this task. The main thing is to choose an adapter with a voltage the same as that of the old device, otherwise you will ruin the entire system, and then even the service center will not be able to help you.To understand where the monitor's power supply is located, you need a tester (multimeter). Use it to measure the voltage on the plug, and from the results you will understand where the “legs grow” from. If the voltage is low or unstable, connect the bulbs in series, about 5-10 W, and check the voltage again. If the adapter is broken, then it will not be able to hold the voltage, or emit a heart-rending whistle. It is better to replace such a power source with a new one right away.Probably every person has a monitor. And they naturally often fail. Therefore, we are constantly asked: what to do if my monitor is broken? If you know a little about technology and have experience in repairing it, then you can try to fix the monitor yourself.For example, let's take the repair of the lg flatron w1943c monitor. In our case, it does not turn on. Image - DIY monitor repair

As usual, we will need: a Phillips screwdriver, a spatula or a plastic card, a soldering iron and a tester (multimeter).

The first step is to remove the front bezel. To do this, just pry it with a spatula or a card.

Next, remove the back cover and see the protective case of the power supply

We disconnect all the cables and raise the protective case of the power supply

In order to remove the board, we need to unscrew the boot from the VGA connector. They are marked in the photo with red circles.

On the board, we found a swollen mains capacitor (marked with a red circle in the photo). After replacing it, everything worked like new.

Now we put everything in the reverse order and use the monitor with pleasure.

As you can see, there is nothing difficult in repairing a monitor with your own hands. Happy repairs and all the best!

Objective: Learn to repair the monitor, what parts need to be replaced if the monitor breaks down

Distortion of the image on the top of the screen: lines are “knocked out”, shifted within a small range

The malfunction appears only at a vertical frequency of 100 Hz at a resolution of 1024 x 768, or at a frequency of 120 Hz at a resolution of 800 x 600.

Replacement of diodes and capacitors (1 μF x 50 V) in the gate circuit of the field-effect transistors S-correction of the raster did not give any result. Oscilloscope control of S-correction signals coming from the microcontroller and switches on field-effect transistors (open-close) showed that all elements are operational.

The reason turned out to be in the increased voltage ripple of 13 V, which is formed by the power supply for the vertical scan driver. This was due to the “loss” of the capacity of the filtering electrolytic capacitor in this circuit.

When turned on, the monitor works, but when you switch it to standby mode (turn on the power saving mode), it does not switch back to working mode (when a video signal appears)

At the same time, the green LED on the front panel is blinking, the power supply is working, the potential of the DPMF & DPMS microcontroller is low.

Replacing the synchroprocessor (TDA 4841), reset chip (KIA 7042), 12 MHz resonator and EEPROM (2408) did not give any result. Replacing the microcontroller solved this problem.

LG T717BKM ALRUEE ”(chassis CA-136)

There is no line sync (see Fig. 1). Synchronization is available only in 1024 x 768 (85 Hz) mode, and a black horizontal stripe 0.5 cm wide appears on the top of the screen. When the signal cable is disconnected, synchronization is also absent. Replacing the microcontroller, EEPROM microcircuit, filtering capacitor along the B + circuit did not give any result. After replacing capacitors C604, C605, C602 (external circuits of the synchroprocessor), synchronization was restored.

Samsung SyncMaster 797DF ”(chassis LE 17ISBB / EDC)

Monitoring the power supply showed that the rectified mains voltage is supplied to the IC601 controller, but there are no secondary voltages at its outputs. After replacing the IC601 microcircuit, the monitor's performance was restored.

Quite often in monitors of this type, the rectifier diode in the secondary circuit of the 14 V power supply fails. As a result, the MT controller switches to the protection mode and there are no secondary voltages at the unit output.

Power supply protection activates when monitor is turned on

All output voltages are greatly underestimated (within 2 ... 4 V), and the voltage at the output of the 50 V channel is 10 ... 20 V. The PWM transistor of the B + Q719 controller is very hot.

Together with it, the filtering capacitor C744 (47 μF x 160 V) heats up. Checking the elements of this unit revealed a faulty diode D710 (UF 4004) - a short circuit. After replacing it, the monitor works normally.

Horizontal image size is abnormal

The problem was solved by replacing the LM358 microcircuit (installed in the horizontal size correction circuit).

Samsung 959NF ”(chassis AQ19NS)

In 20-30 minutes after turning on the monitor, a line shift is observed in the image, and not over the entire raster and with a different amount of shift

Checking the filter capacitor in the mains rectifier, the sweep synchronization circuit with the power supply showed that everything is normal. The filtering capacitor C650 (100 μF x 16 V) installed at the output of the 5 V IC650 voltage regulator turned out to be faulty.

A similar defect often appears in the Samsung SyncMaster 757nf (chassis AQ17NSBU / EDC).

Samtron 56E (chassis PN15VT7L / EDC)

When turned on, a high appears for a second and the protection is triggered

Monitoring of secondary rectifier elements, TDKS showed that everything is normal.

If you disconnect the 50 V voltage circuit from the horizontal scan, the protection does not work.

After replacing the filter capacitor C407 (150uF x 63V), the monitor started working.

The image is indistinct, doubles, and the defect appears even in the image of the on-screen menu and when the video signal source is turned off. When connected to a computer, the image is normal for some time (about 5 minutes), then a crash starts: at first, the image starts to "twitch" along the lines, then the lines are shifted horizontally relative to each other and the "jerking" stops.

The reason turned out to be in the filtering capacitor of voltage B + C402 (10 μF x 250V). It is installed at the output of a DC / DC buck converter using a Q403 transistor.

The monitor does not work, the LED on the front panel is blinking (light color - green)

Monitoring of the secondary circuits showed the presence of a short circuit in the line scan power circuit. The PWM transistor of the controller B + Q719 (breakdown) and the filtering capacitor C740 (leakage) turned out to be faulty.

When the monitor is turned on, the LED on the front panel lights up and turns off after 2-3 seconds. The horizontal scan does not start at this time (there is no high voltage). All voltages of the power supply are normal, replacing the microcontroller and flashing the EEPROM did not give any result

Monitoring the signals at the microcontroller pins showed that there is a low potential at one of the inputs for connecting the K1 keyboard, although not a single button is pressed (there should be a potential of 5 V). The reason was a factory defect: the head of the self-tapping screw fixing the keyboard board shorted the K1 bus to ground. After installing the dielectric washer, the monitor started working

There is no picture. All secondary voltages of the power supply are normal, except for 6.3 V. At the output of this channel, there is only 3.8 V, and if you turn off the kinescope board, the voltage returns to normal - 6.4 V

The reason for the defective capacitor C642 (1000 μF x 16 V) is the loss of capacitance. After replacing it, the image appeared.

Compag p110, Sony gdm-5OOps

The monitor does not turn on, the indicator on the front panel is blinking

The safety resistor R617 (0.47 Ohm) in the 200 V voltage circuit turned out to be open. After replacing it, the monitor started working, but the horizontal raster size was reduced. In addition, there is a vertical raster distortion (S-shaped). All secondary voltages of the PSU were normal, including 200 V.

A faulty capacitor in the C717 dynamic focusing unit (22 μF x 100 V) was identified by the method of element-by-element verification. After replacing it, the image became normal.

Samsung SyncMaster 750s (dp17ls chassis)

The image is blurry. If you adjust the Screen and Focus potentiometers on the TDKS, that is, a normal reaction, the brightness and focus change independently. The supply voltage is normal. EEPROM firmware failed

Sometimes this happens if you confuse the wires during the repair, through which the focusing voltages F1 and F2 are supplied to the CRT board, but not for this case. After replacing these wires, the image became a little clearer, but still abnormal. It turned out that the wires F1 and F2 are not soldered to the CRT panel, but are fixed with spring contacts. After disassembling and cleaning these contacts (there were traces of corrosion), the image returned to normal.

Horizontal size is not adjustable

The adjustment signal is fed from the microcontroller to the base of the Q714 transistor, but is absent from the collector.Element check has identified a faulty transistor Q707 in the S-correction circuit. The diode in the gate circuit of this D707 transistor also turned out to be faulty. After replacing these elements, the horizontal size began to be adjusted.

DIY monitor repair:

1. The first stage: Opening the monitor and initial inspection of the internal components.

First of all, you must disconnect all cables from the monitor. For some monitor models, the signal cable has a permanent external connection to the monitor.

Most LCD monitors have a case with a front frame and a back cover, which often serves as the base of the entire structure. It should be noted that there is no one recommendation for all designs and each manufacturer has its own characteristics inherent only in certain models.

Before opening, you need to take care of a flat surface (for example, a table) and a soft material covering the flat surface and preventing scratches of the LCD matrix. It is also necessary to provide sufficient illumination of the workplace. In order to disassemble the monitor, you will need to separate the stand bracket from the case by unscrewing the mounting screws or self-tapping screws. You will need Phillips screwdrivers such as PH1, PH2, and for some manufacturers' devices, you may need six-star type. It is convenient to use a universal bit holder with a set of replaceable bits of different sizes and types.

After unscrewing and removing the threaded fasteners, it is advisable to remember which fastener was screwed into which hole. The next step is to separate the bezel from the back cover. It should be paid special attention that in many designs - the front frame is attached to the back cover by means of plastic latches. We do not recommend using a slotted screwdriver, a kitchen knife and other unsuitable objects at this stage in order to avoid deformation of the case, the appearance of scoring and chips. We do not recommend using excessive force if the front frame “does not give in” to separation. Careless movement and excessive, incorrectly directed forces can lead to irreparable breakage of the latches, which in turn will lead to unnatural clearances and a change in the appearance of your device.

After removing the front frame, it is necessary to disconnect the connectors of the high-voltage wires on the inverter board going to the LCD panel. We do not recommend pulling the wires in order to avoid breaking the conductors, but to remove the connectors of the high-voltage wires with special tweezers.

There are four main components of an LCD monitor:

Power supply that supplies power to the signal processing unit, LCD module and high-voltage converters (inverters)

Node of high-voltage voltage converters (inverters) of CCFL power supply of backlight lamps.

Signal processing unit. In multimedia monitors, the signal processing unit is much more complex and contains more elements.

LCD module. The structure of the LCD module is described in the article "How the LCD monitor module works"

Before starting the search for the cause of the malfunction, an initial inspection of the nodes should be performed to determine the elements with a changed shape, as well as darkening on the boards, indicating heating of the components. If a component heats up until the board material underneath darkens, this could indicate a component failure or a malfunction in the circuit to which that component belongs.

2. Stage two: Determining the cause of the malfunction

To determine the cause of the malfunction, you will need a device diagram (or a service manual), a multimeter with the functions of dialing, measuring AC and DC voltage, measuring the capacitance of capacitors, as well as an oscilloscope (to diagnose a signal processing unit, a digital oscilloscope with memory may be required)

3. Stage three: Replacing defective components

To replace faulty components, you may need a soldering station with temperature control of the tip, and to replace elements of the signal processing unit - a special hot air soldering station. Note that some microcircuits are sensitive to excessive heat and may fail if overheated. Also, overheating of the pads and tracks should not be allowed, since with excessive heating, delamination and breakage of the conductor on the printed circuit board may occur. If the microcircuits in BGA and FBGA packages are malfunctioning, you may need infrared soldering equipment with an appropriate set of stencils, as well as a special flux.

4. Fourth stage: Post-repair testing

After replacing defective components, a necessary mandatory step is testing after repair. The testing phase will require an electronic thermometer, a DC voltmeter, an ammeter, and a test signal source. The minimum testing time for a restored monitor, according to statistics from practice, is not less than 12 hours. In cases of elimination of malfunctions that appear with warming up or are of an unsystematic nature, the testing time should be increased to 20-30 hours. Testing should take place under the constant supervision of a specialist.

5. Fifth stage: Assembling the monitor

Assembling the monitor should be done in the reverse order of opening. Particular attention should be paid to the screwing force and the length of the screws and self-tapping screws to be screwed in. If the screw or self-tapping screw turns out to be longer, then there is a danger of damage to the housing elements and the LCD panel.

Within the framework of one article, it is impossible to describe all the possible design features and methods of restoring monitors, and in each case, the path to finding the cause of the malfunction is unique. Sometimes an engineer with many years of practical experience has to strain his head to understand the design and circuitry solution.

Video (click to play).

Conclusion: In the course of practical work, I studied theoretical material, learned how to repair a monitor and learned what parts need to be replaced in case of a monitor breakdown, how to repair a monitor with my own hands.

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